Abstract elementary classes stable in ℵ₀

We study abstract elementary classes (AECs) that, in ℵ₀, have amalgamation, joint embedding, no maximal models and are stable (in terms of the number of orbital types). Assuming a locality property for types, we prove that such classes exhibit superstable-like behavior at ℵ₀. More precisely, there is a superlimit model of cardinality ℵ₀ and the class generated by this superlimit has a type-full good ℵ₀-frame (a local notion of nonforking independence) and a superlimit model of cardinality ℵ₁. We also give a supersimplicity condition under which the locality hypothesis follows from the rest.